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Despite their name, there is nothing whimsical about fairy rings -- the common term for dark green rings of grass in a yard. There are two types of fairy rings (Agrocybe spp., Marasmius oreades, Lepiota spp.): edaphic, or non-superficial, and lectophilic, or superficial. Lectophilic rings form when fungus breaks down organic debris on the soil surface and produces nitrogen, giving the grass growing there a greener color than the surrounding area. To remove dark green rings of grass, you have to get rid of their source: a branched, cottony white, thread-like fungal colony growing under the soil surface referred to as mycelium.

1

Cut your grass to just above soil level during a period of vigorous growth, ideally just after the dormant season. Cutting close to the soil gives you access to the thatch layer. Rake the grass trimmings, using a lawn rake, and place them in a lawn waste bag.

2

Water the green ring and the area inside just enough to moisten the soil 1 inch deep. Moisture helps dethatch and aerate the soil.

3

Rake the dark green ring of grass, and the area inside it, starting 2 feet outside of its perimeter, using a dethatching rake. Pull the dethatching rake across the grass in one direction, picking up the rake every few strokes and removing the collected thatch from the tines.

4

Rake the dark green ring of grass, and the area inside it, a second time using the dethatching rake, this time in a direction perpendicular to the first. Rake the loosened thatch from the ground, using a lawn rake, and place the thatch in the bag with the grass trimmings.

5

Run a manual core aerator over the dark green ring, including the area inside it. Push the core aerator in rows as you would a lawn mower, turning around at the end of each row and returning in the opposite direction. Pick up the soil cores and place them in the bag with the thatch and clippings.

6

Insert a sharp spade 1 foot deep in the soil 2 feet outside the perimeter of the dark green ring of grass. Work the spade back and forth when it’s in the ground to loosen the soil.

7

Dig out the dark green ring of grass to a depth of 1 foot, starting outside of the ring where you inserted the spade. Start by digging out a 6-inch-wide, 1-foot-deep trench and looking inside to check the soil for more of the cottony white, thread-like fungus, or mycelium, that causes the ring. Carefully place the soil you dig up in a wheelbarrow, not allowing any of it to fall and touch the ground.

8

Look inside the trench for more of the mycelium. Continue digging until you remove all the mycelium from the ground, placing the infected soil in the wheelbarrow. Make a mental note of how much soil you excavated so you can estimate how much you need to fill the hole later.

9

Dispose of the grass clippings, thatch and soil. Don’t use it for compost. Tie the yard bags securely and give them to your sanitation service when they pick up green waste.

10

Pour enough matured compost and sterile planting soil in a clean wheelbarrow to fill the hole where you dug out the mycelium, plus about 25 percent extra. For example, if you excavated two wheelbarrows-full of infected soil, mix together two-and-a-half wheelbarrows-full of equal parts planting soil and compost.

11

Fill the hole with the soil and compost mixture until it is about 1/2 inch from the surrounding area. Mix two or three handfuls of grass seed, such as perennial ryegrass or Kentucky bluegrass, or a grass seed that matches the other grass in your yard, to the remaining compost and soil mixture.

12

Mix the soil, compost and seed by hand. Add 1 1/4 cups of soluble, slow-release, 4-3-3 NPK starter fertilizer, or a starter fertilizer with a comparable NPK ratio, for every 10 square feet of area to the seed mix and mix again. Cover the area you filled in with enough of the soil, seed and fertilizer mixture to reach 1 to 2 inches above the surrounding soil. Tamp the soil down by walking on it.

13

Water the area you worked, filled and fertilized with 8 to 12 inches of water. Water the area every day with at least 6 inches of water for one week.

Things You Will Need

Lawn mower

Lawn rake

Lawn waste bag

Dethatching rake

Manual core aerator

Spade

Wheelbarrow

Matured compost

Sterile planting soil

Grass seed

Soluble, slow-release 4-3-3 NPK starter fertilizer

Tips

Check the tines -- sometimes referred to as spoons -- of the manual core aerator to see if any get clogged with soil during use. Dig the soil out of the spoons as needed and continue.

About the Author

A.J. Andrews' work has appeared in Food and Wine, Fricote and "BBC Good Food." He lives in Europe where he bakes with wild yeast, milks goats for cheese and prepares for the Court of Master Sommeliers level II exam. Andrews received formal training at Le Cordon Bleu.